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Thanks for the info! If you find any more related information that would be of interest, please post it here.

Here are a few more pictures: I will post some more once I have ploughed my way through the loft and taken the pictures. There should be a 1233 modulator, Thomson 6809 and Siemens RAM and what ever else I come across. Thanks for the pictures! 8-) I'm looking forward to seeing the 'picture of a Siem...

If anyone knows for sure that any of the following information is wrong, please post the correct information. If I understand this correctly, here are the facts: (1) The Dragon and CoCo refresh the RAM in 128 byte chunks ( refresh = read from and write back) (2) It takes the hardware 1.1 millisecond...

This is very much like my first program (posted Sat Jun 20, 2009 7:28 pm) except mine was reading from (and writing to) 12 consecutive addresses each time by default.

I was trying to mimic the behaviour of the hardware refresh (although, after reading the data sheet I realise that I got it wrong). I tried several different variations of both mine and your routine, and they just don't seem to help at all. The computer crashes almost immediately after entering doub...

I had thought that something like this would do the job... 10 ORG $5000 20 LDX #0 30 LDA ,-X 40 LOOP LEAX 256,X 50 LDA ,X 60 CMPX #$7FFF 70 BNE LOOP 70 JMP $9D3D Isn't this doing exactly what the hardware refresh does?

OK, I've done some pretty thorough testing, and the results are better than expected. First I ran the BASIC program and got the following times: NORMAL SPEED = 11.32 DOUBLE SPEED = 5.68 I got the following times after changing the value in line 80 from 49 to 25: NORMAL SPEED = 11.32 DOUBLE SPEED = 5...

The program above will also work OK on a CoCo with some slight modification. You would need to change:- 140 PRINT"NORMAL SPEED =";NS/50 150 PRINT"DOUBLE SPEED =";DS/50 to:- 140 PRINT"NORMAL SPEED =";NS/60 150 PRINT"DOUBLE SPEED =";DS/60 You may also need to change the machine code start address from...

Thanks for the feedback! :) OK, Here's what I've come up with so far... Here's the source code. 10 ORG $5000 20 ORCC #$50 30 LEAX RAMISR,PCR 40 CMPX $10D 50 BEQ BAS 60 LDU $10D 70 STU ROMISR+1,PCR 80 STX $10D 90 BAS RTS 100 RAMISR LDA $76 110 BNE DSPEED 120 STA $FFD8 130 LDA $77 140 STA $76 150 BRA ...

The IRQ is triggered 50 times every second on a standard UK PAL Dragon 32/64. Do you think that resetting the computer back to normal speed for 1/50th of every second would be good enough to keep the RAM refreshed?